Study on time-frequency characteristics and field test of giant magnetostrictive acoustic wave seismic source

Wide-band, high-power and short-residual acoustic wave sources are the key technology for high-resolution detection of large-scale complex structures, in order to solve the contradiction between detection distance and resolution, a new acoustic wave detection instrument is developed by using the acoustic transmitter made of giant magnetostrictive material(GMM) as the source. The focal center frequency is 5 kHz, and the excitation voltage is 300-600 V, it has the characteristics of large radiated sound power, short residual vibration(3.5 cycles) and frequency band width(1-3 kHz), which solves the problem of the high resolution acoustic wave detection. Its greatest advantage is that the acoustic signal generated each time has good consistency, and can be excited by single point and multiple times. The signal-to-noise ratio can be improved by multiple superposition data processing technology. The problem of high-resolution acoustic detection of M-scale structure body has solved the contradiction between acoustic detection distance and resolution, and has been successfully applied to the detection of top coal thickness in coal mine stope. The field survey results show that the high power acoustic wave detection system can reliably extract 4-7 m of reflected wave signals at the interface of deep coal and rock; The wavelet analysis results show that with the help of wavelet multi-resolution analysis to enhance resolution, the accuracy and reliability of top coal thickness detection in stope are improved, it provides an effective way for accurate detection of top coal thickness.